Gas turbine engines operate to produce mechanical work or thrust. Land-based gas turbine engines typically have a generator coupled thereto that uses the mechanical work to drive an electrical generator. In operation, fuel is directed through one or more fuel nozzles to a combustor where it mixes with compressed air and is ignited to form hot combustion gases. These hot combustion gases then pass to a turbine by way of at least one transition duct. The hot combustion gases drive the turbine, which in turn, drives the compressor.
The transition duct, which can often reach temperatures upwards of approximately 1400 deg. Fahrenheit, directs the hot combustion gases from the combustion section to the turbine. Depending on the type of engine, the combustor may be located radially outward of the turbine and the engine may comprise a plurality of combustors. In this arrangement, the transition duct changes radial position along its length between the combustor and the turbine. Regardless of geometry, the transition duct requires a sufficient amount of cooling to overcome the elevated operating temperatures and maintain metal temperatures of the transition duct such that the base materials can withstand the mechanical and thermal stresses. There is yet another issue with respect to cooling of a plurality of transition ducts that feed the turbine inlet. When multiple transition ducts having impingement sleeves are positioned adjacent to each other, there is often times little space for cooling air to pass between the transition duct impingement sleeves. The smaller space causes the cooling air that does pass between adjacent transition ducts to move at a higher velocity than would normally be desired in order to achieve effective cooling. As such, the cooling is not as effective in these regions as other locations along the transition duct. In order to improve cooling to the transition duct, FIGS. 1 and 2 depict a gas turbine transition duct 100 in accordance with the prior art where a plurality of semi-hemispherical flow catching devices 102 are used to divert cooling air into a passageway 104 of the transition duct 100.